The invention relates to an apparatus for moulding plastic products, said apparatus comprising at least two plastic moulding machines each of which comprises a robot for transferring a moulded product from the moulding machine onto a conveyor belt.
Apparatuses of this kind are well known. Moulding machines are typically injection moulding machines. They are used, for example, for moulding parts of plastic enclosures. Each injection moulding machine is typically used for moulding one type of products, e.g. the bottom or the cover of a plastic enclosure; after the moulding, the parts are combined to form a plastic enclosure.
Moulded products must satisfy certain quality criteria--often rather strict ones--as regards the surface, for example. The quality of products can often be quite easily determined on the basis of ocular assessment when the products are on the conveyor belt to which they are ejected from the injection moulding machine. Since there are several injection moulding machines located in different parts of the factory hall, the person responsible for quality inspection must go from one machine to another; this is because it is not sensible to have different persons inspecting the quality of products produced by the different injection moulding machines. In practice, the person responsible for quality inspection has to "run" from one machine to another. Another factor that makes it more difficult to do the job rationally is that the moulding time, i.e. the time it takes to manufacture a product, is different at the different injection moulding machines: one machine may use e.g. two seconds for the manufacture of a product, another one may use eight seconds, yet another one needs nine seconds, etc. On account of this, the person responsible for quality inspection must go to the different injection moulding machines at different intervals, depending on the machine and the product.
On account of the arrangement described above, a defect in the quality of a product is detected at a relatively late stage. An injection moulding machine may mould a large number of defective products before the defect is detected and the machine is stopped so that the necessary steps can be taken to correct the defect.
Another problem associated with known apparatuses comprising several moulding machines is removing products from the machines and transporting them for further treatment or packaging. This requires that either a motor-driven forklift or a hand pallet truck is used for collecting the moulded products, which are normally piled on a pallet, separately from each moulding machine. When there are several injection moulding machines located in different parts of the factory hall, the truck has to travel relatively long distances, which not only consumes time and energy but also increases the risk of accidents.
Yet another problem with apparatuses comprising several moulding machines is that they take up a lot of floor area in a factory hall. It has not been possible to mount the machines close to each other, since narrow passages between the machines would complicate the transport of moulded products with a forklift.